1. Field of the Invention
The present invention relates to an improvement in a melting and holding furnace for processing aluminum and other metals.
2. Description of the Prior Art
In the melting and holding furnace, a raw material of aluminum is fed to a preheating tower, and heated and melted in a melting chamber continuous with the tower. Molten aluminum is then transferred to a holding chamber communicating with the melting chamber, where the molten aluminum is heated by a sustaining burner to be maintained at a selected temperature. The molten aluminum is removed little by little, for casting, from a well communicating with the holding chamber.
The holding chamber of the conventional melting and holding furnace for carrying out the above melting operation has a flat bottom, which entails the following disadvantages:
I. Low-temperature melt flows from the melting chamber to the holding chamber, and from the holding chamber directly into the well. This lowers the melt temperature in the well. PA1 II. As a result of the low-temperature melt flowing from the melting chamber to the holding chamber, iron, silicon and other substances are deposited in the holding chamber. These substances flow into the well and mix into products to form hard spots or otherwise impair the product quality. PA1 III. The melt immediately after leaving the melting chamber contains a large amount of gas such as hydrogen gas. Castings formed of such melt have a high fraction defective. PA1 (1) Aluminum raw material fed into a preheating tower is melted in the melting chamber continuous with the tower. PA1 (2) Molten material formed in the melting chamber is allowed to flow into the holding chamber. At this time the molten material is at a low temperature immediately above its boiling point. PA1 (3) The molten material is heated to a selected temperature by a sustaining burner. While being heated, the molten material flows zigzag along the submerged banks in the holding chamber and toward the well. PA1 (4) In the course of such movement, the molten material releases gases and leaves deposits along the banks, whereby the molten material as stabilized is supplied to the well. PA1 (5) The stabilized molten material is removed little by little from the well to be used for casting.